Disclosed are methods and kits for identifying and characterizing polynucleotide sequences in a sample which may include a heterogeneous sample. Some of the methods and kits are directed to the identification and characterization of a virus in a sample, which may include HIV capable of cause AIDS or AIDS-like symptoms. The virus may be HIV-1, and may also include drug resistant mutations. The methods may include reacting a mixture that includes, in addition to nucleic acid isolated from the sample, at least one oligonucleotide capable of specifically hybridizing to HIV nucleic acid where the oligonucleotide includes at least one non-natural base. In addition, the methods may include detection of one or more mutations in HIV nucleic acid that are associated with drug resistance.